They’re a family they see tia as their little sis
She's their lil sis, not stuck up despite being smarter, tried to protect them when the imperial knights tried to cath them on the first prince's order and it's not shown in the manhwa but in the novel it's mentioned that Tia spends most of her free time in Shannet's part of the house reading or playing with the twins since Gallahan started working on the Cororoy textile and his garments shop. So it's only natural they developed such deep bond with her.
Yess, they mentioned it on novel and that is so cuteee
Yes Tia frequently goes there, I'm just amazed because on her past life the twins disregards/ignores her They are just so precious and all the Lombardy grandchildren are getting along beside belsac and astallius
But I wonder why they are so loyal and fond of Tia?? Like, I get that they got interested when Tia fought back to Belsac from the first few chapters, but they are so (over)protective and they love Tia so much